Recently, due to environmental concerns, such as global warming arising from the emission of carbon dioxide and energy issues of the depletion of oil resources, studies focusing on ammonia as an alternative clean energy source as a substitute for hydrocarbon fuels have been carried out, and for example, it is proposed to obtain motor power by combusting ammonia gas in an internal combustion engine. In this regard, Japanese Unexamined Patent Publication (Kokai) No. 5-332152 describes that hydrogen, in addition to ammonia, is combusted in an internal combustion engine in order to improve the combustion performance of ammonia. In addition, Japanese Unexamined Patent Publication (Kokai) No. 5-332152 proposes an ammonia-burning internal combustion engine having an ammonia-decomposing reaction means which decomposes ammonia by use of the heat of exhaust gas after the combustion of ammonia in the internal combustion engine, and a hydrogen-storing alloy which accumulates hydrogen gas obtained by the ammonia-decomposing reaction means.